Obama's Half-Brother Will Be Trump's Debate Guest

As Donald Trump and Hillary Clinton prepare to spar during the third and final presidential debate, Trump has continued his tradition of inviting controversial guests.

As an attack on the sitting president, the campaign has invited the half-brother of President Barack Obama, Malik, to attend the debate as Trump's guest, ABC News has confirmed. The news was first reported by the New York Post.

Malik Obama, a native Kenyan, has been an outspoken critic of Clinton and said that his support is with Trump.

But Trump must overcome his own vulnerabilities in this debate at a time when at least eight women have accused him of groping or sexually assaulting them. (Trump has vehemently denied all the accusations.) Campaign aides say that the Trump to appear tomorrow will be an aggressive one, poised to attack.

At a campaign rally in Grand Junction, Colorado, Trump hinted at what was to come.

"Tomorrow night's going to be interesting. Now she's home sleeping and I'm working so -- it's the way it's going to be in the White House too. She'd be sleeping, I'd be working," he said.

Whereas Trump was criticized for a lack of preparation before the first debate, sources tell ABC News that sessions have been more focused this time around.

Senior level sources say Sunday was a return to debate prep at Trump's weekend retreat -- his golf course in Bedminster, New Jersey. Aides describe a rapid-fire question session led in part by New Jersey Gov. Chris Christie. Christie, sources say, served as Trump's sparring partner, the one to fire back at Trump what Clinton would potentially say, though there were no mock debates held.

Trump has also had a rotating cast of characters assisting him, from Republican National Committee Chair Reince Priebus to former New York City Mayor Rudy Giuliani, sources say. On Monday, Trump was peppered with rapid-fire questions surrounding national security, with Alabama Sen. Jeff Sessions assisting.

The Republican nominee felt confident about his last performance, sources say. One senior source says the goal for tomorrow night is to reassure the faith of the Republican base.

But some worry Trump has muddied the waters of his message by touting unsubstantiated claims that the election will be "rigged," proclaiming that the media, the establishment and his accusers are set to steal the election from him.

He has intensified his calls to be on the lookout for voter fraud, encouraging his crowds to keep a wary eye, especially in urban communities. And, in Wisconsin on Monday, Trump warned that the voters to look out for are the ones who are no longer alive.

"More than 1.8 million deceased individuals right now are listed as voters. Oh, that's wonderful. Well, if they are going to vote for me, we'll think about it, right. But I have a feeling they are not going to for me," he said.

In an interview with ABC News' Tom Llamas, Trump also criticized the speaker of the House, Paul Ryan, a member of the party Trump is trying to win, theorizing that Ryan doesn't want Trump to win the election.

"Well, maybe not, because maybe he wants to run in four years or maybe he doesn't know how to win. Maybe just doesn't know how to win," Trump said.

But advisers are confident that Trump will be focused tomorrow night. "He's fired up," a senior source said.